Multiple transmission time interval coordination with time division duplexing

ABSTRACT

Methods, systems, and devices for wireless communication are described. Data may be received during transmission time intervals (TTIs) that have a short duration relative to other TTIs. The short-duration TTIs may occur within or overlap a longer duration TTI, such as a subframe. Feedback responsive to the data may be generated and assigned for transmission during an uplink TTI according to a feedback timing or delay, which may be selected to reduce latency or balance the payload size of uplink messages sent during the assigned uplink TTI. Data and feedback assignments in short-duration TTIs may be configured based on a time division duplexing (TDD) configuration for some TTIs (e.g., subframes). TTIs that are a Long Term Evolution (LTE) subframe, an LTE slot, and a duration of two LTE symbol periods may be supported. Portions of special TTIs may be used for transmissions according to shorter-duration TTIs.

CROSS REFERENCES

The present Application for Patent is a Continuation of U.S. patentapplication Ser. No. 16/358,042 by Patel et al., entitled “MultipleTransmission Time Interval Coordination With Time Division Duplexing”filed Mar. 19, 2019, assigned U.S. Pat. No. 10,959,216 with an issuedate of Mar. 23, 2021, which is a Divisional of U.S. patent applicationSer. No. 15/592,850 by Patel et al., entitled “Multiple TransmissionTime Interval Coordination With Time Division Duplexing,” filed May 11,2017, assigned U.S. Pat. No. 10,548,118 with an issue date of Jan. 28,2020, which claims priority to U.S. Provisional Patent Application No.62/336,511 by Patel et al., entitled “Multiple Transmission TimeInterval Coordination With Time Division Duplexing,” filed May 13, 2016,each of which are assigned to the assignee hereof and expresslyincorporated by reference herein in their entirety.

BACKGROUND

The following relates generally to wireless communication and morespecifically to multiple transmission time interval (TTI) coordinationwithin a time division duplexing (TDD) configuration.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems. A wireless multiple-accesscommunications system may include a number of base stations, eachsimultaneously supporting communication for multiple communicationdevices, which may be otherwise known as user equipment (UE).

Wireless multiple-access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis Long Term Evolution (LTE). LTE is designed to improve spectralefficiency, lower costs, improve services, make use of new spectrum, andbetter integrate with other open standards. LTE may use OFDMA on thedownlink (DL), single-carrier frequency division multiple access(SC-FDMA) on the uplink (UL), and multiple-input multiple-output (MIMO)antenna technology.

Within multiple access systems, methods for error control (e.g., hybridautomatic repeat request (HARQ)) may provide feedback regarding thesuccess of a transmission. In some cases, data received using TTIs of ashort duration relative to other TTIs, feedback may correspondingly beprovided in a short duration TTI. However, a timing between datareception and feedback transmission may result in unnecessarycommunication delays and reduced system performance if the timing doesnot account for the durations of the TTIs associated with the data andfeedback.

SUMMARY

The described techniques provide for efficient feedback timing, such ashybrid automatic repeat request (HARQ) timing, in a system supportingmultiple transmission time intervals (TTI) in a time division duplexing(TDD) configuration. A device, such as a user equipment (UE), operatingaccording to the TDD configuration may receive data during TTIs thathave a short duration relative to other TTIs. The short-duration TTIsmay occur within or overlap a longer duration TTI, such as a subframe.The device may generate feedback responsive to the data and may assignthe feedback for transmission during an uplink TTI according to afeedback timing or delay. The feedback timing may be selected or imposedby the system to reduce latency or balance the payload size of uplinkmessages sent during the assigned uplink TTI.

By way of example, a wireless device may receive data during one or moreshort TTIs during a downlink subframe. HARQ feedback may be generatedbased on the data and may be assigned to an uplink TTI according to apredetermined feedback timing. In some cases, feedback timing mayinclude an additional delay factor to balance the payload size foruplink messages sent during the uplink TTIs. Additionally oralternatively, transmissions may be coordinated or adjusted to accountfor a TDD configuration. For example, a short-duration TTI may be withina guard period or an uplink pilot signal (UpPTS) of a special subframeand may be used for transmitting the feedback. In some case, a UE'scapabilities or timing advance condition, or both, along with a feedbacktiming, may be evaluated or used to identify TTIs of a TDD configurationfor communications with the UE.

A method of wireless communication in a system that supports a TDDconfiguration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. The methodmay include receiving first data during a first TTI of the secondduration and second data during a second TTI of the second duration. Themethod may also include generating first feedback for the first data andsecond feedback for the second data, assigning the first feedback andthe second feedback to an uplink TTI of the first duration in the TDDconfiguration based at least in part on a feedback timing associatedwith TTIs of the second duration, and transmitting the first feedbackand the second feedback during the uplink TTI of the first duration.

An apparatus for wireless communication in a system that supports a TDDconfiguration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include means for receiving first data during a first TTIof the second duration and second data during a second TTI of the secondduration. The apparatus may also include means for generating firstfeedback for the first data and second feedback for the second data,means for assigning the first feedback and the second feedback to anuplink TTI of the first duration in the TDD configuration based at leastin part on a feedback timing associated with TTIs of the secondduration, and means for transmitting the first feedback and the secondfeedback during the uplink TTI of the first duration.

Another apparatus for wireless communication in a system that supports aTDD configuration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable when executed by the processor to cause theapparatus to receive first data during a first TTI of the secondduration and second data during a second TTI of the second duration,generate first feedback for the first data and second feedback for thesecond data, assign the first feedback and the second feedback to anuplink TTI of the first duration in the TDD configuration based at leastin part on a feedback timing associated with TTIs of the secondduration, and transmit the first feedback and the second feedback duringthe uplink TTI of the first duration.

A non-transitory computer readable medium storing code for wirelesscommunication in a system that supports a TDD configuration with TTIs ofa first duration and TTIs of a second duration that is less than thefirst duration is described. The code may include instructionsexecutable to receive first data during a first TTI of the secondduration and second data during a second TTI of the second duration,generate first feedback for the first data and second feedback for thesecond data, assign the first feedback and the second feedback to anuplink TTI of the first duration in the TDD configuration based at leastin part on a feedback timing associated with TTIs of the secondduration, and transmit the first feedback and the second feedback duringthe uplink TTI of the first duration.

Another method of wireless communication in a system that supports a TDDconfiguration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. The methodmay include identifying an uplink pilot time slot (UpPTS) of a specialTTI of the first duration in the TDD configuration, identifying a TTI ofthe second duration during the UpPTS, and transmitting an uplink messageduring the TTI of the second duration.

Another apparatus for wireless communication in a system that supports aTDD configuration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include means for identifying an uplink pilot time slot(UpPTS) of a special TTI of the first duration in the TDD configuration,means for identifying a TTI of the second duration during the UpPTS, andmeans for transmitting an uplink message during the TTI of the secondduration.

Another apparatus for wireless communication in a system that supports aTDD configuration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable, when executed by the processor, to causethe apparatus to identify an UpPTS of a special TTI of the firstduration in the TDD configuration, identify a TTI of the second durationduring the UpPTS, and transmit an uplink message during the TTI of thesecond duration.

Another non-transitory computer-readable medium storing code forwireless communication in a system that supports a TDD configurationwith TTIs of a first duration and TTIs of a second duration that is lessthan the first duration is described. The code may include instructionsoperable to cause a processor to identify an UpPTS of a special TTI ofthe first duration in the TDD configuration, identify a TTI of thesecond duration during the UpPTS, and transmit an uplink message duringthe TTI of the second duration.

Another method of wireless communication in a system that supports a TDDconfiguration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. The methodmay include transmitting first data during a first TTI of the secondduration and second data during a second TTI of the second duration,identifying an uplink TTI of the first duration in the TDD configurationbased at least in part on a feedback timing associated with TTIs of thesecond duration, and receiving first feedback for the first data andsecond feedback for the second data during the uplink TTI of the firstduration.

Another apparatus for wireless communication in a system that supports aTDD configuration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include means for transmitting first data during a firstTTI of the second duration and second data during a second TTI of thesecond duration, means for identifying an uplink TTI of the firstduration in the TDD configuration based at least in part on a feedbacktiming associated with TTIs of the second duration, and means forreceiving first feedback for the first data and second feedback for thesecond data during the uplink TTI of the first duration.

Another apparatus for wireless communication in a system that supports aTDD configuration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable when executed by the processor to cause theapparatus to transmit first data during a first TTI of the secondduration and second data during a second TTI of the second duration,identify an uplink TTI of the first duration in the TDD configurationbased at least in part on a feedback timing associated with TTIs of thesecond duration, and receive first feedback for the first data andsecond feedback for the second data during the uplink TTI of the firstduration.

Another non-transitory computer-readable medium storing code forwireless communication in a system that supports a TDD configurationwith TTIs of a first duration and TTIs of a second duration that is lessthan the first duration is described. The code may include instructionsoperable to cause a processor to transmit first data during a first TTIof the second duration and second data during a second TTI of the secondduration, identify an uplink TTI of the first duration in the TDDconfiguration based at least in part on a feedback timing associatedwith TTIs of the second duration, and receive first feedback for thefirst data and second feedback for the second data during the uplink TTIof the first duration.

Another method of wireless communication in a system that supports a TDDconfiguration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. The methodmay include restricting one or more TTIs of the first duration in theTDD configuration for communication with a subset of user equipment(UEs) in the system based at least in part on a delay metric, schedulingthe subset of UEs according to the restriction of the one or more TTIsof the first duration, and communicating with the subset of UEs in oneor more TTIs of the second duration based at least in part on thescheduling.

Another apparatus for wireless communication in a system that supports aTDD configuration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include means for restricting one or more TTIs of thefirst duration in the TDD configuration for communication with a subsetof user equipment (UEs) in the system based at least in part on a delaymetric, means for scheduling the subset of UEs according to therestriction of the one or more TTIs of the first duration, and means forcommunicating with the subset of UEs in one or more TTIs of the secondduration based at least in part on the scheduling.

Another apparatus for wireless communication in a system that supports aTDD configuration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable when executed by the processor to cause theapparatus to restrict one or more TTIs of the first duration in the TDDconfiguration for communication with a subset of user equipment (UEs) inthe system based at least in part on a delay metric, schedule the subsetof UEs according to the restriction of the one or more TTIs of the firstduration, and communicate with the subset of UEs in one or more TTIs ofthe second duration based at least in part on the scheduling.

Another non-transitory computer-readable medium storing code forwireless communication in a system that supports a TDD configurationwith TTIs of a first duration and TTIs of a second duration that is lessthan the first duration is described. The code may include instructionsoperable to cause a processor to restrict one or more TTIs of the firstduration in the TDD configuration for communication with a subset ofuser equipment (UEs) in the system based at least in part on a delaymetric, schedule the subset of UEs according to the restriction of theone or more TTIs of the first duration, and communicate with the subsetof UEs in one or more TTIs of the second duration based at least in parton the scheduling.

Another method of wireless communication in a system that supports a TDDconfiguration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. The methodmay include identifying an UpPTS of a special TTI of the first durationin the TDD configuration, identifying a TTI of the second durationduring the UpPTS, and receiving an uplink control or data message duringthe TTI of the second duration from a first UE.

Another apparatus for wireless communication in a system that supports aTDD configuration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include means for identifying an UpPTS of a special TTI ofthe first duration in the TDD configuration, means for identifying a TTIof the second duration during the UpPTS, and means for receiving anuplink control or data message during the TTI of the second durationfrom a first UE.

Another apparatus for wireless communication in a system that supports aTDD configuration with TTIs of a first duration and TTIs of a secondduration that is less than the first duration is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable, when executed by the processor, to causethe apparatus to identify an UpPTS of a special TTI of the firstduration in the TDD configuration, identify a TTI of the second durationduring the UpPTS, and receive an uplink control or data message duringthe TTI of the second duration from a first UE.

Another non-transitory computer-readable medium storing code forwireless communication in a system that supports a TDD configurationwith TTIs of a first duration and TTIs of a second duration that is lessthan the first duration is described. The code may include instructionsoperable to cause a processor to identify an UpPTS of a special TTI ofthe first duration in the TDD configuration, identify a TTI of thesecond duration during the UpPTS, and receive an uplink control or datamessage during the TTI of the second duration from a first UE.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrates an example of a wireless communications systemthat supports multiple transmission time interval (TTI) coordinationwithin a time division duplexing (TDD) configuration in accordance withaspects of the present disclosure;

FIGS. 3 through 6 illustrate an example of a TDD configuration thatsupports multiple TTI coordination within a TDD configuration inaccordance with aspects of the present disclosure;

FIGS. 7 and 8 illustrate an example of process flow for multiple TTIcoordination within a TDD configuration in accordance with aspects ofthe present disclosure;

FIGS. 9 through 11 show block diagrams of a device that supportsmultiple TTI coordination within a TDD configuration in accordance withaspects of the present disclosure;

FIG. 12 illustrates a block diagram of a system including a userequipment (UE) that supports multiple TTI coordination within a TDDconfiguration in accordance with aspects of the present disclosure;

FIGS. 13 through 15 show block diagrams of a device or devices thatsupport multiple TTI coordination within a TDD configuration inaccordance with aspects of the present disclosure;

FIG. 16 illustrates a block diagram of a system including a device thatsupports multiple TTI coordination within a TDD configuration inaccordance with aspects of the present disclosure;

FIGS. 17 through 21 show flowcharts illustrating methods for multipleTTI coordination within a TDD configuration in accordance with aspectsof the present disclosure.

DETAILED DESCRIPTION

Shortened transmission time intervals (TTIs) may allow for reducedturnaround time and a shorter hybrid automatic repeat request (HARQ)feedback delay. In some cases, TTIs that have a reduced durationrelative to other TTIs of a system may facilitate latency reduction forsome operations. Predetermined delays associated with HARQ feedback maybe applied based on shortened or reduced-duration TTIs (e.g., slot TTIsor two-symbol TTIs rather than 1 ms TTIs) in low latency systems. Thefeedback delay may also be based on balancing considerations. Forexample, a timing between downlink data and responsive feedback may beselected to achieve an even load of HARQ feedback over multiple uplink(UL) TTIs. In some cases, a feedback timing or delay may be increasedbeyond a predetermined time period to even the feedback load across theTTIs of the next UL period (e.g., one or more UL TTIs within one or moreUL subframes). HARQ feedback or uplink control channel load balancingmay accordingly allow for improved UL channel design by limitingvariable or large format maximum in uplink payload sizes.

In some cases, feedback timing, or a delay between data reception andcorresponding uplink feedback, may be directly or indirectly based on auser equipment (UE) capability, modulation and coding scheme (MCS), or atiming advance (TA). For example, downlink (DL) TTIs may be scheduled toaccount for a UE TA, UE processing capabilities, or a MCS (e.g., a highMCS may be associated with additional processing time). That is, UEsthat have a higher TA, or that benefit from additional processing time,may be scheduled before UEs that may respond with feedback after ashorter time period. Further, a special subframe may be utilized tosupport short TTI HARQ feedback. For example, a short TTI during a guardperiod and/or an uplink pilot signal (UpPTS) may be used fortransmitting the HARQ feedback.

Aspects of the disclosure introduced above are described below in thecontext of a wireless communication system. Specific examples of HARQfeedback timing configurations are then described. Aspects of thedisclosure are further illustrated by and described with reference toapparatus diagrams, system diagrams, and flowcharts that relate to titleof the application.

FIG. 1 illustrates an example of a wireless communications system 100that supports multiple TTI coordination within a time division duplexing(TDD) configuration in accordance with aspects of the presentdisclosure. The wireless communications system 100 includes basestations 105, UEs 115, and a core network 130. In some examples, thewireless communications system 100 may be a Long Term Evolution (LTE) orLTE-Advanced network. Wireless communications system 100 may support ashortened a TDD configuration based on a reduced TTI duration.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude UL transmissions from a UE 115 to a base station 105, or DLtransmissions, from a base station 105 to a UE 115. UEs 115 may bedispersed throughout the wireless communications system 100, and each UE115 may be stationary or mobile. A UE 115 may also be referred to as amobile station, a subscriber station, a remote unit, a wireless device,an access terminal (AT), a handset, a user agent, a client, or liketerminology. A UE 115 may also be a cellular phone, a wireless modem, ahandheld device, a personal computer, a tablet, a personal electronicdevice, a machine-type communication (MTC) device, etc.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., S1, etc.). Base stations105 may communicate with one another over backhaul links 134 (e.g., X2,etc.) either directly or indirectly (e.g., through core network 130).Base stations 105 may perform radio configuration and scheduling forcommunication with UEs 115, or may operate under the control of a basestation controller (not shown). In some examples, base stations 105 maybe macro cells, small cells, hot spots, or the like. Base stations 105may also be referred to as eNodeBs (eNBs) 105.

Carriers may transmit bidirectional communications using frequencydivision duplexing (FDD) (e.g., using paired spectrum resources) or TDD(e.g., using unpaired spectrum resources). Frame structures orconfigurations for FDD (e.g., frame structure type 1) and TDD (e.g.,frame structure type 2) may be defined. Use of TDD may offer flexibledeployments without paired UL-DL spectrum resources. For TDD framestructures, each subframe may carry UL or DL traffic, and specialsubframes may be used to switch between DL and UL transmission.Allocation of UL and DL subframes within radio frames may be symmetricor asymmetric and may be statically determined or may be reconfiguredsemi-statically. Special subframes may carry DL traffic (e.g., viadownlink pilot time slot (DwPTS)) or UL traffic (e.g., via uplink pilottime slot (UpPTS)) and may include a Guard Period (GP) between DL and ULtraffic. Switching from UL to DL traffic may be achieved by setting a TAat the UE 115 without the use of special subframes or a guard period.

Time intervals in LTE may be expressed in multiples of a basic time unit(e.g., the sampling period, T_(s)=1/30,720,000 seconds). Time resourcesmay be organized according to radio frames of length of 10 ms(T_(f)=307200 Ts), which may be identified by a system frame number(SFN) ranging from 0 to 1023. Each frame may include ten 1 ms subframesnumbered from 0 to 9. A subframe may be further divided into two 0.5 msslots, each of which contains 6 or 7 modulation symbol periods(depending on the length of the cyclic prefix prepended to each symbol).Excluding the cyclic prefix, each symbol contains 2048 sample periods.

A frame structure may be used to organize physical resources. A framemay be a 10 ms interval that may be further divided into 10 equallysized sub-frames. Each sub-frame may include two consecutive time slots.Each slot may include six or seven orthogonal frequency divisionmultiple access (OFDMA) symbol periods. A resource element consists ofone symbol period and one subcarrier (a 15 KHz frequency range). Aresource block may contain 12 consecutive subcarriers in the frequencydomain and, for a normal cyclic prefix in each orthogonalfrequency-division multiplexing (OFDM) symbol, 7 consecutive OFDMsymbols in the time domain (1 slot), or 84 resource elements. Someresource elements may include DL reference signals (DL-RS). The DL-RSmay include a cell-specific reference signal (CRS) and a UE-specific RS(UE-RS). UE-RS may be transmitted on the resource blocks associated on aphysical downlink shared channel (PDSCH). The number of bits carried byeach resource element may depend on the modulation scheme (theconfiguration of symbols that may be selected during each symbolperiod). Thus, the more resource blocks that a UE receives and thehigher the modulation scheme, the higher the data rate may be.

A TTI may be defined as the smallest unit of time in which a basestation 105 may schedule a UE 115 for UL or DL transmission. Forexample, if a UE 115 is receiving DL data, then during each TTI a basestation 105 may assign resources and indicate (via downlink controltransmissions) to the UE 115 where to look for its DL data. In somecases, a subframe may be the basic unit of scheduling or TTI. In othercases, such as with low latency operation, a different, reduced-durationTTI (e.g., a short TTI) may be used. A reduced-duration or short TTI mayhave a duration of a symbol period, a pair of symbol periods, a slot(i.e., half of a subframe), or other durations less than 1 ms. TTIs forlow latency operation may thus have a numerology that is compatible withother LTE transmission structures and timing (e.g., subframe). Thewireless communications system 100 may concurrently supportcommunication using TTIs over different duration (e.g., TTIs having aduration of a subframe and TTIs having a duration of a symbol period ora slot).

Wireless communications system 100 may support communications accordingto a protocol organized into different layers. At the physical layer, aphysical downlink control channel (PDCCH) may carry downlink controlinformation (DCI) in control channel elements (CCEs), which may consistof nine logically contiguous resource element groups (REGs), where eachREG contains 4 resource elements (REs). DCI includes informationregarding DL scheduling assignments, UL resource grants, transmissionscheme, UL power control, HARQ information, MCS and other information. Aphysical uplink control channel (PUCCH) may be used for ULacknowledgements (ACKs), scheduling requests (SRs) and channel qualityindicators (CQI) and other UL control information. A PUCCH may be mappedto a control channel defined by a code and two consecutive resourceblocks. UL control signaling may depend on the presence of timingsynchronization for a cell. PUCCH resources for scheduling request (SR)and CQI reporting may be assigned (and revoked) through radio resourcecontrol (RRC) signaling.

Within wireless communications system 100 or similar systems, HARQ maybe a method of ensuring that data is received correctly over acommunication link 125. HARQ may include a combination of errordetection (e.g., using a cyclic redundancy check (CRC)), forward errorcorrection (FEC), and retransmission (e.g., automatic repeat request(ARQ)). The chain of transmission, response and retransmission may bereferred to as a HARQ process. HARQ may improve throughput at the mediumaccess control (MAC) layer in poor radio conditions (e.g.,signal-to-noise conditions). In Incremental Redundancy HARQ, incorrectlyreceived data may be stored in a buffer and combined with subsequenttransmissions to improve the overall likelihood of successfully decodingthe data.

The response in a HARQ process may include an ACK indicating asuccessful attempt to decode information and a negative-acknowledgement(NACK) indicating a failed attempt to decode the information. In somecases, redundancy bits are added to each message prior to transmission.This may be useful in poor conditions. In other cases, redundancy bitsare not added to each transmission, but are retransmitted after thetransmitter of the original message receives a NACK indicating a failedattempt to decode the information. The chain of transmission, responseand retransmission may be referred to as a HARQ process. In some cases,a limited number of HARQ processes may be used for a given communicationlink 125. A time delay may determine or dictate when HARQ feedback istransmitted on the UL. That is, the TTI scheduled for HARQ feedbacktransmission may be associated with a predetermined delay (e.g.,feedback timing) from the DL reception TTI.

To maintain synchronization with the base station 105, the UE 115 maytransmit based on a TA value. The TA value may account for signalpropagation delay due to the geographic distance between a UE 115 andthe base station 105. The base station 105 or the UE 115 may determinethe signal propagation delay. In an example, TA may change over time asthe physical distance between a UE 115 and the base station 105 changes.When the UE 115 and base station 105 are geographically closer, thesignal propagation delay may be shorter and, when geographically fartherapart, the signal propagation delay may be longer. The UE 115 may usethe TA value to determine when to send a signal such that the basestation 105 receives the signal at the correct time along a timeline inaccordance with the reception of other signals from other UEs 115.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including: wider bandwidth, shorter symbol duration, shorterTTIs, and modified control channel configuration. In some cases, an eCCmay be associated with a carrier aggregation configuration or a dualconnectivity configuration (e.g., when multiple serving cells have asuboptimal or non-ideal backhaul link). An eCC may also be configuredfor use in unlicensed spectrum or shared spectrum (where more than oneoperator is allowed to use the spectrum). An eCC characterized by widebandwidth may include one or more segments that may be utilized by UEs115 that are not capable of monitoring the whole bandwidth or prefer touse a limited bandwidth (e.g., to conserve power).

An eCC may utilize a different symbol duration than other CCs, which mayinclude use of a reduced symbol duration as compared with symboldurations of the other CCs. A shorter symbol duration is associated withincreased subcarrier spacing. A device, such as a UE 115 or base station105, utilizing eCCs may transmit wideband signals (e.g., 20, 40, 60, 80MHz, etc.) at reduced symbol durations (e.g., 16.67 microseconds). A TTIin eCC may consist of one or multiple symbols. In some cases, the TTIduration (that is, the number of symbols in a TTI) may be variable. Insome cases, an eCC may utilize a different symbol duration than otherCCs, which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration isassociated with increased subcarrier spacing. A device, such as a UE 115or base station 105, utilizing eCCs may transmit wideband signals (e.g.,20, 40, 60, 80 MHz, etc.) at reduced symbol durations (e.g., 16.67microseconds). A TTI in eCC may consist of one or multiple symbols. Insome cases, the TTI duration (that is, the number of symbols in a TTI)may be variable.

HARQ timing in wireless communications system 100 may vary with ordepend on a TTI duration used for communication. UEs 115 operating in aTDD configuration may receive data during short-duration TTIs (e.g.,two-symbol or 1-slot). The short-duration TTIs may occur within oroverlap a longer-duration TTI, such as a subframe. UEs 115 may generatefeedback responsive to the data and may assign the feedback fortransmission during an uplink TTI according to a feedback timing ordelay. The feedback timing may be selected or imposed by wirelesscommunications system 100 to reduce latency or balance the payload sizeof uplink messages sent during the assigned uplink TTI.

FIG. 2 illustrates an example of a wireless communications system 200that supports multiple TTI coordination within a TDD configuration inaccordance with aspects of the present disclosure. In some cases,wireless communications system 200 may represent aspects of techniquesperformed by a UE 115 or base station 105 as described with reference toFIG. 1 .

Wireless communications system 200 may be an example of a shortened TTIsystem employing bidirectional communications using TDD. An example basestation 105-a and UE 115-a may support shortened TTI HARQ feedback overcommunication link 125-a. DL subframes 205 may include DL TTIs 220,special subframes 210 may include special TTIs 225, and UL subframes 215may include UL TTIs 230.

In some cases, a HARQ feedback timing may be based on a shortened TTIduration (e.g., a slot TTI or two-symbol TTI). A shortened TTI (e.g., DLTTIs 220, special TTIs 225, and UL TTIs 230) may allow for reducedturnaround time and a shorter HARQ feedback delay. HARQ feedback delaysassociated with other wireless communication systems (e.g.,predetermined time period delays associated with subframe durations) maybe applied to shortened TTIs in low latency systems. The predeterminedtime may be a number, k, TTIs after a DL TTI 220. For example, HARQtiming may follow an N+k rule where N is the DL TTI 220 and N+k is thesoonest TTI available for HARQ feedback (e.g., if N+k is an UL TTI 230).That is, if N is DL TTI 220-a and k=4, HARQ feedback may be handled byUL TTI 230-a, as UL TTI 230-a is the next TTI available for UL and alsosatisfies the N+4 rule. In some cases, a two-symbol DL TTI and one-slotUL TTI system may support HARQ feedback using shortened TTIs. Forexample, UL slot TTIs may carry two-symbol TTI transmissions from a DLsubframe 205 (e.g., UL slot TTIs carry seven (7) two-symbol TTIs from aprevious DL subframe).

Using a short TTI HARQ feedback may result in shorter HARQ timing gapsor delays. According to predetermined delays, utilization of a slot TTI(e.g., 0.5 ms) or a two-symbol TTI (e.g., approximately 0.143 ms or 0.16ms depending on a 14 symbol or 12 symbol subframe) may offer shorterHARQ gaps than a subframe TTI (e.g., 1 ms). For example, the last columnof table 1 illustrates the reduced timing gaps associated with a slotTTI. The first two columns indicate a DL TTI and a corresponding UL TTI(e.g., after the arrow) that handles the HARQ feedback of the DL TTI. Afirst number indicates a subframe (e.g., a TTI in the first column) anda number following a dash indicates a short TTI (e.g., in the secondcolumn where a TTI is shorter than a subframe). A number in parenthesisindicates a HARQ timing gap associated with the feedback. For an LTEType 1 TDD frame configuration, which may include downlink subframes atindices 0, 4, 5, and 9, uplink subframes at indices 2, 3, 7, and 8, andspecial subframes at indices 1 and 6, the HARQ timing information may bedepicted in Table 1.

TABLE 1 Example HARQ timing savings for a Slot TTI Subframe TTI HARQTiming (1 ms) Slot TTI (0.5 ms) Gap Savings { 0 → 7 }(7 ms) { 0-1 → 2-1}(2 ms) & 5 ms { 0-2 → 2-2 }(2 ms) { 1 → 7 }(6 ms) { 1-1 → 3-1 }(2 ms) 4ms { 4 → 8 }(4 ms) { 4-1 → 7-1 }(3 ms) & 1 ms and 1.5 ms { 4-2 → 7-1}(2.5 ms) { 5 → 2 }(7 ms) { 5-1 → 7-1 }(2 ms) & 5 ms {5-2 → 7-2 }(2 ms){ 6 → 2 }(6 ms) { 6-1 → 8-1 }(2 ms) 4 ms { 9 → 3 }(4 ms) { 9-1 → 2-1 }(3ms) & 1 ms and 1.5 ms { 9-2 → 2-1 }(2.5 ms)

Table 2 illustrates the comparison between subframe TTI and two-symbolTTI (e.g., in a 7 symbol per slot configuration) HARQ feedback, andfollows the same conventions as Table 1:

TABLE 2 Example HARQ timing savings for a Two-Symbol TTI Subframetwo-symbol DL TTI HARQ TTI (~0.143 ms) Timing (1 ms) Slot UL TTI (0.5ms) Gap Savings { 0 → 7 }(7 ms) { 0-1,0-2,0-3,0-4,0-5,0-6,0-7 → ~5.5 ms2}(~1.5 ms) { 1 → 7 }(6 ms) { 1-1,1-2,1-3,1-4,1-5,1-6,1-7 → ~5.25 ms  2}(~0.75 ms) { 4 → 8 }(4 ms) { 4-1,4-2,4-3,4-4,4-5,4-6,4-7 → ~1.5 ms 7}(~2.5 ms) { 5 → 2 }(7 ms) { 5-1,5-2,5-3,5-4,5-5,5-6,5-7 → ~5.5 ms 7}(~1.5 ms) { 6 → 2 }(6 ms) { 6-1,6-2,6-3,6-4,6-5,6-6,6-7 → ~5.25 ms  7}(~0.75 ms) { 9 → 3 }(4 ms) { 9-1,9-2,9-3,9-4,9-5,9-6,9-7 → ~1.5 ms 2}(~2.5 ms)

A delay period may be further based on an attempt to balance an evenload of HARQ feedback over multiple UL TTIs 230 (e.g., slots). That is,a HARQ feedback delay may be increased beyond a predetermined timeperiod in order to balance the feedback load across the TTIs of the nextUL period (e.g., one or more UL TTIs 230 within an UL subframe 215).HARQ feedback load balancing may allow for improved channel design.Specifically, less variability in HARQ feedback load may allow for moreefficient channel design (e.g., of a PUCCH) resulting from lessstringent constraints arising from the ability to support less variablechannel payloads. HARQ timing according to shortened TTIs may result inincreased benefit when used in a carrier aggregation (CA) scheme.

The delay period may further be based on a UE capability or TA. That is,short TTIs in different transmission instances in TDD may have differentHARQ timing and may result in different tolerances of UL TAs. Near cellusers with smaller TA may be scheduled in the latter part of a DLsubframe 205 while cell edge users may be scheduled earlier in a DLsubframe 205 due to a larger TA. Additionally or alternatively, high MCSmay use more processing capability and may be scheduled earlier. Formore stringent cases, the slot-TTI may have 3-slot for HARQ feedbackprocessing. A small TA (e.g., less than 10 us) may ensure enough timefor processing. However, if by design and/or TDD limitations a DL slotTTI transmission has a response time of more than 3-slot, the TAtolerance level may be correspondingly increased. For example, a 4-slotHARQ timing delay may tolerate at least 500 us TA and a 5-slot HARQtiming delay may tolerate 667 us TA (e.g., a max TA). Therefore, if a UE115 has a large TA and/or has lower processing capability, ultra-lowlatency (ULL) may be supported for the UE 115 in restricted short TTItransmission instances such that the HARQ timing delay is at least4-slot (e.g., or 5-slot). Similar considerations may be applied fortwo-symbol TTI scenarios.

A special subframe 210 may also be used to support short TTI HARQfeedback. For example, additional symbols or TTIs may be prepended to aUpPTS region (e.g., special TTI 225) of a special subframe 210 to conveyuplink transmissions (e.g., HARQ feedback and channel state information(CSI)). For example, if N is DL TTI 220-a and k is 4, HARQ feedback maybe handled by special TTI 225-a, as special TTI 225-a is the next TTIavailable for UL and also satisfies the N+4 rule. ULL users may knowadditional symbols are added or scheduled in front of the UpPTS and maymake use of them for short TTI HARQ feedback. In some cases, if aconfigured sounding reference signal (SRS) is configured for a portionof the UpPTS symbol length, the remaining portion may be used fortransmitting HARQ feedback, CSI, and/or uplink data (on, e.g., a PUCCHor physical uplink shared channel (PUSCH)). In these cases, backwardscompatibility may be maintained. That is, non-ULL users may still usethe symbols for SRS while ULL users may multiplex onto the UpPTS regionfor the transmissions described above. Therefore, a portion of the ULportion of a special subframe 210 may be repurposed, or a prependedregion for short TTI may be added for shortened control or data (e.g.,short TTI HARQ feedback).

FIG. 3 illustrates an example of a TDD configuration 300 that supportsmultiple TTI coordination within a TDD configuration in accordance withaspects of the present disclosure. In some cases, TDD configuration 300may represent aspects of techniques performed by a UE 115 or basestation 105 as described with reference to FIGS. 1 and 2 .

TDD configuration 300 illustrates HARQ feedback using shortened TTIsaccording to a predetermined delay. In TDD configuration 300, DLsubframes 305 may include DL TTIs 320, special subframes 310 may includespecial TTIs 325, and UL subframes 315 may include UL TTIs 330.Different TDD configurations may have a different ordering of DL, UL,and special subframes. In TDD configuration 300, a given TTI may beassociated with a subframe number, the number of the TTI within thesubframe, and the directionality of the subframe. For example, DL TTI320-b is the second TTI within the ninth subframe (e.g., 9-2) in thedownlink direction (e.g., D).

The example illustrated in TDD configuration 300 assumes a predetermineddelay rule of N+k with k=4. For DL TTI 320-d (e.g., the second DL TTI ofsubframe 0) the TTI that satisfies the N+4 rule is UL TTI 330-b and thushandles the HARQ feedback associated with DL TTI 320-d. Additionally, asdescribed above, the TTI that handles HARQ feedback may be a TTIsuitable for UL transmissions. For example, for DL TTI 320-a (e.g., DLTTI 9-1) the TTI that satisfies the N+4 rule is special TTI 325-a.However, UL TTI 330-a may handle the HARQ feedback associated with DLTTI 320-a as it is the next TTI suitable for UL.

Similarly, the HARQ feedback for DL TTI 320-b and DL TTI 320-c may alsobe handled by UL TTI 330-a. According to the method described above,HARQ feedback may be handled by the earliest available TTI and mayresult in unbalanced handling of HARQ feedback (e.g., UL TTI 330-ahandles HARQ feedback for 3 DL TTIs 320 and UL TTI 330-b handles HARQfeedback for 1 DL TTI 330).

FIG. 4 illustrates an example of a TDD configuration 400 that supportsmultiple TTI coordination within a TDD configuration in accordance withaspects of the present disclosure. In some cases, TDD configuration 400may represent aspects of techniques performed by a UE 115 or basestation 105 as described with reference to FIGS. 1 and 2 .

TDD configuration 400 illustrates balanced HARQ feedback using shortenedTTIs according to a predetermined delay. In TDD configuration 400, DLsubframes 405 may include DL TTIs 420, special subframes 410 may includespecial TTIs 425, and UL subframes 415 may include UL TTIs 430.Different TDD configurations may have a different ordering of DL, UL,and special subframes. In TDD configuration 400, a given TTI may beassociated with a subframe number, the number of the TTI within thesubframe, and the directionality of the subframe. For example, DL TTI420-b is the second TTI within the ninth subframe (e.g., 9-2) in thedownlink direction (e.g., D).

The example illustrated in TDD configuration 400 assumes at least apredetermined delay rule of N+k with k=4. Further, TDD configuration 400may employ additional delay for UL TTI HARQ feedback balancing. Forexample, HARQ feedback for DL TTI 420-a and DL TTI 420-b may be handledby UL TTI 430-a and HARQ feedback for DL TTI 420-d may be handled by ULTTI 430-b similar to the method described in FIG. 3 . However, HARQfeedback for DL TTI 420-c may have an additional delay (e.g., a delay inaddition to an N+k delay) in order to balance the HARQ feedback on theUL TTIs 430 of UL subframe 415-a. That is, the HARQ feedback for DL TTI420-c may be handled by UL TTI 430-b (e.g., instead of UL TTI 430-aaccording to the N+k rule alone) such that the HARQ feedback on UL TTI430-a and UL TTI 430-b is balanced. For example, uplink controlmessages, such as a low latency PUCCHs, transmitted in UL TTI 430-a andUL TTI 430-b may have a same payload size or capacity, which may bereferred to as balanced size.

FIG. 5 illustrates an example of a TDD configuration 500 that supportsmultiple TTI coordination within a TDD configuration in accordance withaspects of the present disclosure. In some cases, TDD configuration 500may represent aspects of techniques performed by a UE 115 or basestation 105 as described with reference to FIGS. 1 and 2 .

TDD configuration 500 illustrates balanced HARQ feedback using shortenedTTIs of different lengths according to a predetermined delay. In TDDconfiguration 500, DL subframes 505 may include DL TTIs 520, specialsubframes 510 may include special TTIs 525, and UL subframes 515 mayinclude UL TTIs 530. Different TDD configurations may have a differentordering of DL, UL, and special subframes. In TDD configuration 500, agiven TTI may be associated with a subframe number, the number of theTTI within the subframe, and the directionality of the subframe. Forexample, DL TTI 520-b is the second TTI within the ninth subframe (e.g.,9-2) in the downlink direction (e.g., D). DL TTIs 520 may be two-symbolTTIs while UL TTIs 530 may be slot TTIs.

The example illustrated in TDD configuration 500 assumes at least apredetermined delay rule of N+k with k=4. Further, TDD configuration 500may employ additional delay for UL TTI HARQ feedback balancing. Forexample, all DL TTIs 520 (e.g., all 7 DL TTIs 520 for a 14 symbol persubframe configuration) in DL subframe 505-a (e.g., subframe 9) may haveHARQ feedback handled by UL TTI 530-a. HARQ feedback for all DL TTIs 520in DL subframe 505-b may be handled by UL TTI 530-b. Accordingly, theHARQ feedback (e.g., ACK/NACK payload) is balanced across the UL TTIs530 of UL subframe 515-a (e.g., subframe 2).

FIG. 6 illustrates an example of a TDD configuration 600 that supportsmultiple TTI coordination within a TDD configuration in accordance withaspects of the present disclosure. In some cases, TDD configuration 600may represent aspects of techniques performed by a UE 115 or basestation 105 as described with reference to FIGS. 1 and 2 .

TDD configuration 600 illustrates HARQ feedback using shortened TTIsaccording to a predetermined delay with use of special subframe TTIs. InTDD configuration 600, DL subframes 605 may include DL TTIs 620, specialsubframes 610 may include special TTIs 625, and UL subframes 615 mayinclude UL TTIs 630. Different TDD configurations may have a differentordering of DL, UL, and special subframes. In TDD configuration 600, agiven TTI may be associated with a subframe number, the number of theTTI within the subframe, and the directionality of the subframe. Forexample, DL TTI 620-b is the second TTI within the ninth subframe (e.g.,9-2) in the downlink direction (e.g., D).

The example illustrated in TDD configuration 300 assumes a predetermineddelay rule of N+k with k=4. Additionally, TDD configuration 600 mayallow for use of UL TTIs at the beginning of a special subframe 610. Forexample, the HARQ feedback for DL TTI 620-a may be handled by specialTTI 625-a. However, special TTI 625-b may not be an UL TTI (e.g., UpPTS)and may not be used for HARQ feedback handling. Therefore, a portion ofthe UL portion of a special subframe 610-a may be repurposed, or aprepended region for short TTI (e.g., special TTI 625-a) may be addedfor shortened control or data (e.g., DL TTI 620-a HARQ feedback). HARQfeedback for DL TTI 620-b and DL TTI 620-c may be handled by UL TTI630-a, while HARQ feedback for DL TTI 630-d may be handled by UL TTI630-b according to methods described with reference to FIGS. 2-5 .

FIG. 7 illustrates an example of process flow 700 for multiple TTIcoordination within a TDD configuration in accordance with aspects ofthe present disclosure. In some cases, process flow 700 may representaspects of techniques performed by a UE 115 or base station 105 asdescribed with reference to FIGS. 1 and 2 . Process flow 700 depicts anexample of feedback generation and assigning of UL short TTIs fortransmission of feedback.

At 705-a UE 115-b may optionally transmit an indication of a UE specificdelay parameter to base station 105-b. Additionally or alternatively, at705-b, base station 105-b may optionally transmit an indication of a UEspecific parameter. The UE specific parameter may indicate whensubsequent data is to be received at UE 115-b.

At 710, base station 105-b may transmit data during a first TTI. At 715,base station may transmit data during a second TTI. UE 115-b may receivethe data during the respective first and second DL TTIs (e.g., a slotTTI, two-symbol TTI, etc.). The first and second TTI may be short TTIsand, in some cases, may be within the same subframe. In some cases, thedata may be received based on the indication in 705-a and/or 705-b.

At 720, UE 115-b may generate feedback for the data received at 710 and715. The feedback may be HARQ feedback associated with data received ineach of the two TTIs.

At 725, UE 115-b may assign feedback associated with each of the two DLTTIs to an UL subframe. The UL subframe may be assigned according tofeedback timing associated with the DL TTIs. That is, UL TTIs (e.g., aslot TTI, two-symbol TTI, etc.) within the UL subframe may be assignedaccording to the location of the DL TTI the data was received in. Insome cases, the UL TTIs may be assigned to balance the payload of thefeedback or messages associated with the data received in the two DLTTIs. That is, each UL TTI may be assigned feedback associated with thesame number of DL TTIs.

At 730, UE 115-b may transmit the first data to base station 105-bduring the UL TTI assigned in 725. At 735, UE 115-b may transmit thesecond data to base station 105-b during the UL TTI assigned at 725.

FIG. 8 illustrates an example of process flow 800 for multiple TTIcoordination within a TDD configuration in accordance with aspects ofthe present disclosure. In some cases, process flow 800 may representaspects of techniques performed by a UE 115 or base station 105 asdescribed with reference to FIGS. 1 and 2 . Process flow 800 depicts anexample of identifying and using short TTIs within a special subframefor feedback reporting.

At 805, UE 115-c may identify a UpPTS of a special subframe. Optionally,at 810, UE 115-c may identify a guard period of a special subframe.

At 815, UE 115-c may identify a short TTI during the UpPTS. Optionally,at 820, UE 115-c may identify a short TTI during the guard period.

At 825, UE 115-c may transmit an UL message during the TTI of the UpPTS.In some cases, the UL message of 825 may be transmitted during a TTIthat includes a portion of the UpPTS and a portion of an UL TTI.Optionally, at 830, UE 115-c may transmit an UL message during the TTIof the guard period.

FIG. 9 shows a block diagram 900 of a device 905 that supports multipleTTI coordination within a TDD configuration in accordance with variousaspects of the present disclosure. Device 905 may be an example ofaspects of a UE 115 as described with reference to FIGS. 1 and 2 .Device 905 may include receiver 910, UE TTI coordination manager 915,and transmitter 920. Device 905 may also include a processor. Each ofthese components may be in communication with one another (e.g., via oneor more buses).

Receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to multiple TTIcoordination within a TDD configuration, etc.). Information may bepassed on to other components of the device. The receiver 910 may be anexample of aspects of the transceiver 1240 as described with referenceto FIG. 12 . Receiver 910 may receive first data during a first TTI ofthe second duration and second data during a second TTI of the secondduration. In some cases, the first duration is one LTE subframe. In somecases, the second duration is one LTE slot. In some cases, the secondduration is two LTE symbol periods.

UE TTI coordination manager 915 may generate first feedback for thefirst data and second feedback for the second data, assign the firstfeedback and the second feedback to an uplink TTI of the first durationin the TDD configuration based on a feedback timing associated with TTIsof the second duration, identify an UpPTS of a special TTI of the firstduration in the TDD configuration, and identify a TTI of the secondduration during the UpPTS.

Transmitter 920 may transmit signals generated by other components ofthe device. In some examples, the transmitter 920 may be collocated witha receiver 910 in a transceiver module. For example, the transmitter 920may be an example of aspects of the transceiver 1240 as described withreference to FIG. 12 . The transmitter 920 may include a single antenna,or it may include a set of antennas. Transmitter 920 may transmit thefirst feedback and the second feedback during the uplink TTI of thefirst duration, transmit an uplink message during the TTI of the secondduration, transmit an additional uplink message during the additionalTTI of the second duration, and transmit an uplink message during a timeperiod that includes a portion of the UpPTS and a portion of an uplinkTTI of the first duration in the TDD subframe configuration.

FIG. 10 shows a block diagram 1000 of a device 1005 that supportsmultiple TTI coordination within a TDD configuration in accordance withvarious aspects of the present disclosure. Device 1005 may be an exampleof aspects of a device 905 or a UE 115 as described with reference toFIGS. 1, 2 and 9 . Device 1005 may include receiver 1010, UE TTIcoordination manager 1015, and transmitter 1020. Device 1005 may alsoinclude a processor. Each of these components may be in communicationwith one another (e.g., via one or more buses).

Receiver 1010 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to multiple TTIcoordination within a TDD configuration, etc.). Information may bepassed on to other components of the device. The receiver 1010 may be anexample of aspects of the transceiver 1240 as described with referenceto FIG. 12 .

UE TTI coordination manager 1015 may be an example of aspects of the UETTI coordination manager 915 as described with reference to FIG. 9 . UETTI coordination manager 1015 may also include feedback component 1025and special subframe component 1030.

Feedback component 1025 may generate first feedback for the first dataand second feedback for the second data and assign the first feedbackand the second feedback to an uplink TTI of the first duration in theTDD configuration based on a feedback timing associated with TTIs of thesecond duration. Special subframe component 1030 may identify an UpPTSof a special TTI of the first duration in the TDD configuration andidentify a TTI of the second duration during the UpPTS.

Transmitter 1020 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1020 may be collocatedwith a receiver 1010 in a transceiver module. For example, thetransmitter 1020 may be an example of aspects of the transceiver 1240 asdescribed with reference to FIG. 12 . The transmitter 1020 may include asingle antenna, or it may include a set of antennas.

FIG. 11 shows a block diagram 1100 of a UE TTI coordination manager 1115that supports multiple TTI coordination within a TDD configuration inaccordance with various aspects of the present disclosure. The UE TTIcoordination manager 1115 may be an example of aspects of a UE TTIcoordination manager 915, a UE TTI coordination manager 1015, or a UETTI coordination manager 915 as described with reference to FIGS. 9 and10 . The UE TTI coordination manager 1115 may include feedback component1125 and special subframe component 1130. Each of these modules maycommunicate, directly or indirectly, with one another (e.g., via one ormore buses).

Feedback component 1125 may generate first feedback for the first dataand second feedback for the second data and assign the first feedbackand the second feedback to an uplink TTI of the first duration in theTDD configuration based on a feedback timing associated with TTIs of thesecond duration. Special subframe component 1130 may identify an UpPTSof a special TTI of the first duration in the TDD configuration andidentify a TTI of the second duration during the UpPTS.

Feedback balancing component 1135 may identify a first portion of theuplink TTI of the first duration based on a location of the first TTI ofthe second duration, where the first feedback is transmitted in a firstuplink message during the first portion of the uplink TTI of the firstduration and identify a second portion of the uplink TTI of the firstduration based on a location of the second TTI of the second duration,where the second feedback is transmitted in a second uplink messageduring the second portion of the uplink TTI of the first duration. Insome cases, a payload size of the first uplink message and a payloadsize of the second uplink message are balanced.

In some cases, the location of the first TTI of the second durationincludes a first downlink TTI of the first duration in the TDDconfiguration and the location of the second TTI of the second durationincludes a second downlink TTI of the first duration in the TDDconfiguration, and where the first portion of the uplink TTI of thefirst duration is designated for feedback associated with the firstdownlink TTI of the first duration and the second portion of the uplinkTTI of the first duration is designated for feedback associated with thesecond downlink TTI of the first duration. In some cases, the firstportion and the second portion of the uplink TTI of the first durationare designated for feedback associated with a same number of TTIs of thesecond duration.

Feedback timing component 1140 may identify a timer period fortransmitting feedback. In some cases, the feedback timing associatedwith TTIs of the second duration is an integer multiple of TTIs of thesecond duration.

Delay indication component 1145 may transmit an indication of a UEspecific delay parameter to a base station, where the first data or thesecond data is received based on the UE specific delay parameter andreceive an indication of a UE specific delay parameter from a basestation, where the first data or the second data is received based onthe UE specific delay parameter. Guard period component 1150 mayidentify a guard period during the special TTI of the first duration andidentify an additional TTI of the second duration during the guardperiod.

FIG. 12 shows a diagram of a system 1200 including a device 1205 thatsupports multiple TTI coordination within a TDD configuration inaccordance with various aspects of the present disclosure. Device 1205may be an example of a device 905, device 1005, or a UE 115 as describedabove, e.g., with reference to FIGS. 1, 2, 9 and 10 .

Device 1205 may include components for bi-directional voice and datacommunications including components for transmitting and receivingcommunications, including UE TTI coordination manager 1215, processor1225, memory 1230, software 1235, transceiver 1240, antenna 1245, andeCC module 1250.

Processor 1225 may include an intelligent hardware device, (e.g., acentral processing unit (CPU), a microcontroller, an applicationspecific integrated circuit (ASIC), etc.) Memory 1230 may include randomaccess memory (RAM) and read only memory (f). The memory 1230 may storecomputer-readable, computer-executable software 1235 includinginstructions that, when executed, cause the processor to perform variousfunctions described herein. In some cases, the memory 1230 can contain,among other things, a Basic Input-Output system (BIOS) which may controlbasic hardware and/or software operation such as the interaction withperipheral components or devices.

Software 1235 may include code to implement aspects of the presentdisclosure, including code to support multiple TTI coordination within aTDD configuration. Software 1235 can be stored in a non-transitorycomputer-readable medium such as system memory or other memory. In somecases, the software 1235 may not be directly executable by the processorbut may cause a computer (e.g., when compiled and executed) to performfunctions described herein.

Transceiver 1240 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1240 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1240 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas. In some cases, thewireless device may include a single antenna 1245. However, in somecases the device may have more than one antenna 1245, which may becapable of concurrently transmitting or receiving multiple wirelesstransmissions.

eCC module 1250 may enable operations using enhanced component carriers(eCCs) including operations using low latency TTIs and operations inunlicensed spectrum.

FIG. 13 shows a block diagram 1300 of a device 1305 that supportsmultiple TTI coordination within a TDD configuration in accordance withvarious aspects of the present disclosure. Device 1305 may be an exampleof aspects of a base station 105 as described with reference to FIGS. 1and 2 . Device 1305 may include receiver 1310, base station TTIcoordination manager 1315, and transmitter 1320. Device 1305 may alsoinclude a processor. Each of these components may be in communicationwith one another (e.g., via one or more buses).

Receiver 1310 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to multiple TTIcoordination within a TDD configuration, etc.). Information may bepassed on to other components of the device. The receiver 1310 may be anexample of aspects of the transceiver 1240 as described with referenceto FIG. 12 . Receiver 1310 may receive first feedback for the first dataand second feedback for the second data during the uplink TTI of thefirst duration and receive an uplink control or data message during theTTI of the second duration from a first UE.

Base station TTI coordination manager 1315 may be an example of aspectsof the base station TTI coordination manager 1615 as described withreference to FIG. 16 . Base station TTI coordination manager 1315 mayidentify an uplink TTI of the first duration in the TDD configurationbased on a feedback timing associated with TTIs of the second duration,restrict one or more TTIs of the first duration in the TDD configurationfor communication with a subset of user equipment (UEs) in the systembased on a delay metric, schedule the subset of UEs according to therestriction of the one or more TTIs of the first duration, identify anUpPTS of a special TTI of the first duration in the TDD configuration,and identify a TTI of the second duration during the UpPTS.

Transmitter 1320 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1320 may be collocatedwith a receiver 1310 in a transceiver module. For example, thetransmitter 1320 may be an example of aspects of the transceiver 1240 asdescribed with reference to FIG. 12 . The transmitter 1320 may include asingle antenna, or it may include a set of antennas. Transmitter 1320may transmit first data during a first TTI of the second duration andsecond data during a second TTI of the second duration and communicatewith the subset of UEs in one or more TTIs of the second duration basedon the scheduling.

FIG. 14 shows a block diagram 1400 of a device 1405 that supportsmultiple TTI coordination within a TDD configuration in accordance withvarious aspects of the present disclosure. Device 1405 may be an exampleof aspects of a device 1305 or a base station 105 as described withreference to FIGS. 1, 2 and 13 . Device 1405 may include receiver 1410,base station TTI coordination manager 1415, and transmitter 1420. Device1405 may also include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

Receiver 1410 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to multiple TTIcoordination within a TDD configuration, etc.). Information may bepassed on to other components of the device. The receiver 1410 may be anexample of aspects of the transceiver 1240 as described with referenceto FIG. 12 .

Base station TTI coordination manager 1415 may be an example of aspectsof the base station TTI coordination manager 1615 as described withreference to FIG. 16 . Base station TTI coordination manager 1415 mayalso include feedback timing component 1425, scheduling restrictioncomponent 1430, scheduling component 1435, and special subframecomponent 1440.

Feedback timing component 1425 may identify an uplink TTI of the firstduration in the TDD configuration based on a feedback timing associatedwith TTIs of the second duration.

Scheduling restriction component 1430 may restrict one or more TTIs ofthe first duration in the TDD configuration for communication with asubset of user equipment (UEs) in the system based on a delay metric. Insome cases, the delay metric includes at least one of a timing advanceparameter, a location parameter, a processing speed parameter, a UEcategory, or a modulation and coding scheme parameter, or anycombination thereof. Scheduling component 1435 may schedule the subsetof UEs according to the restriction of the one or more TTIs of the firstduration.

Special subframe component 1440 may identify an UpPTS of a special TTIof the first duration in the TDD configuration and identify a TTI of thesecond duration during the UpPTS.

Transmitter 1420 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1420 may be collocatedwith a receiver 1410 in a transceiver module. For example, thetransmitter 1420 may be an example of aspects of the transceiver 1240 asdescribed with reference to FIG. 12 . The transmitter 1420 may include asingle antenna, or it may include a set of antennas.

FIG. 15 shows a block diagram 1500 of a base station TTI coordinationmanager 1515 that supports multiple TTI coordination within a TDDconfiguration in accordance with various aspects of the presentdisclosure. The base station TTI coordination manager 1515 may be anexample of aspects of a base station TTI coordination manager 1315, abase station TTI coordination manager 1415, or a base station TTIcoordination manager 1615 as described with reference to FIGS. 13, 14,and 16 . The base station TTI coordination manager 1515 may includefeedback timing component 1525, scheduling restriction component 1530,scheduling component 1535, and special subframe component 1540. Each ofthese modules may communicate, directly or indirectly, with one another(e.g., via one or more buses).

Feedback timing component 1525 may identify an uplink TTI of the firstduration in the TDD configuration based on a feedback timing associatedwith TTIs of the second duration.

Scheduling restriction component 1530 may restrict one or more TTIs ofthe first duration in the TDD configuration for communication with asubset of user equipment (UEs) in the system based on a delay metric. Insome cases, the delay metric includes at least one of a timing advanceparameter, a location parameter, a processing speed parameter, a UEcategory, or a modulation and coding scheme parameter, or anycombination thereof. Scheduling component 1535 may schedule the subsetof UEs according to the restriction of the one or more TTIs of the firstduration.

Special subframe component 1540 may identify an UpPTS of a special TTIof the first duration in the TDD configuration and identify a TTI of thesecond duration during the UpPTS.

Feedback balancing component 1545 may identify a first portion of theuplink TTI of the first duration based on a location of the first TTI ofthe second duration, where the first feedback is received in a firstuplink message during the first portion of the uplink TTI of the firstduration and identify a second portion of the uplink TTI of the firstduration based on a location of the second TTI of the second duration,where the second feedback is received in a second uplink message duringthe second portion of the uplink TTI of the first duration.

In some cases, a payload size of the first uplink message and a payloadsize of the second uplink message are balanced. In some cases, thelocation of the first TTI of the second duration includes a firstdownlink TTI of the first duration in the TDD configuration and thelocation of the second TTI of the second duration includes a seconddownlink TTI of the first duration in the TDD configuration, and wherethe first portion of the uplink TTI of the first duration is designatedfor feedback associated with the first downlink TTI of the firstduration and the second portion of the uplink TTI of the first durationis designated for feedback associated with the second downlink TTI ofthe first duration.

Delay indication component 1550 may receive an indication of a UEspecific delay parameter from a UE, where the first data or the seconddata is transmitted based on the UE specific delay parameter andtransmit an indication of a UE specific delay parameter to a UE, wherethe first data or the second data is transmitted based on the UEspecific delay parameter. In some cases, the UE specific delay parameterincludes a timing advance parameter, a location parameter, a processingspeed parameter, a UE category, or a modulation and coding schemeparameter.

SRS component 1555 may receive a SRS from a second UE during the UpPTS,second UE is communicating according to TTIs of the first duration, andwhere the uplink control or data message from the first UE ismultiplexed with the SRS from the second UE.

FIG. 16 illustrates a block diagram of a system 1600 including a device1605 that supports multiple TTI coordination within a TDD configurationin accordance with various aspects of the present disclosure. Device1605 may be an example of a device 1305, device 1405, or a base station105 as described above, e.g., with reference to FIGS. 1, 2, 13 and 14 .

Device 1605 may include components for bi-directional voice and datacommunications including components for transmitting and receivingcommunications, including base station TTI coordination manager 1615,processor 1625, memory 1630, software 1635, transceiver 1640, antenna1645, network communications manager 1650, and base stationcommunications manager 1655.

Processor 1625 may include an intelligent hardware device, (e.g., a CPU,a microcontroller, an ASIC, etc.) Memory 1630 may include RAM and ROM.The memory 1630 may store computer-readable, computer-executablesoftware 1635 including instructions that, when executed, cause theprocessor to perform various functions described herein. In some cases,the memory 1630 can contain, among other things, a BIOS which maycontrol basic hardware and/or software operation such as the interactionwith peripheral components or devices.

Software 1635 may include code to implement aspects of the presentdisclosure, including code to support multiple TTI coordination within aTDD configuration. Software 1635 can be stored in a non-transitorycomputer-readable medium such as system memory or other memory. In somecases, the software 1635 may not be directly executable by the processorbut may cause a computer (e.g., when compiled and executed) to performfunctions described herein.

Transceiver 1640 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1640 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1640 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas. In some cases, thewireless device may include a single antenna 1645. However, in somecases the device may have more than one antenna 1645, which may becapable of concurrently transmitting or receiving multiple wirelesstransmissions.

Network communications manager 1650 may manage communications with thecore network (e.g., via one or more wired backhaul links). For example,the network communications manager 1650 may manage the transfer of datacommunications for client devices, such as one or more UEs 115.

Base station communications manager 1655 may manage communications withother base station 105, and may include a controller or scheduler forcontrolling communications with UEs 115 in cooperation with other basestations 105. For example, the base station communications manager 1655may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, base station communications manager 1655may provide an X2 interface within an LTE/LTE-A wireless communicationnetwork technology to provide communication between base stations 105.

FIG. 17 shows a flowchart illustrating a method 1700 for multiple TTIcoordination within a TDD configuration in accordance with variousaspects of the present disclosure. The operations of method 1700 may beimplemented by a UE 115 or its components as described herein. Forexample, the operations of method 1700 may be performed by a UE TTIcoordination manager as described with reference to FIGS. 9 through 11 .In some examples, a UE 115 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware.

At block 1705, the UE 115 may receive first data during a first TTI ofthe second duration and second data during a second TTI of the secondduration. The operations of block 1705 may be performed according to themethods as described with reference to FIG. 2 . In some examples,aspects of the operations of block 1705 may be performed by a receiveras described with reference to FIGS. 9 through 11 .

At block 1710, the UE 115 may generate first feedback for the first dataand second feedback for the second data. The operations of block 1710may be performed according to the methods as described with reference toFIG. 2 . In some examples, aspects of the operations of block 1710 maybe performed by a feedback component as described with reference toFIGS. 9 through 11 .

At block 1715, the UE 115 may assign the first feedback and the secondfeedback to an uplink TTI of the first duration in the TDD configurationbased on a feedback timing associated with TTIs of the second duration.The operations of block 1715 may be performed according to the methodsas described with reference to FIG. 2 . In some examples, aspects of theoperations of block 1715 may be performed by a feedback component asdescribed with reference to FIGS. 9 through 11 .

At block 1720, the UE 115 may transmit the first feedback and the secondfeedback during the uplink TTI of the first duration. The operations ofblock 1720 may be performed according to the methods as described withreference to FIG. 2 . In some examples, aspects of the operations ofblock 1720 may be performed by a transmitter as described with referenceto FIGS. 9 through 11 .

FIG. 18 shows a flowchart illustrating a method 1800 for multiple TTIcoordination within a TDD configuration in accordance with variousaspects of the present disclosure. The operations of method 1800 may beimplemented by a UE 115 or its components as described herein. Forexample, the operations of method 1800 may be performed by a UE TTIcoordination manager as described with reference to FIGS. 9 through 11 .In some examples, a UE 115 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware.

At block 1805, the UE 115 may identify an UpPTS of a special TTI of thefirst duration in the TDD configuration. The operations of block 1805may be performed according to the methods as described with reference toFIG. 2 . In some examples, aspects of the operations of block 1805 maybe performed by a special subframe component as described with referenceto FIGS. 9 through 11 .

At block 1810, the UE 115 may identify a TTI of the second durationduring the UpPTS. The operations of block 1810 may be performedaccording to the methods as described with reference to FIG. 2 . In someexamples, aspects of the operations of block 1810 may be performed by aspecial subframe component as described with reference to FIGS. 9through 11 .

At block 1815, the UE 115 may transmit an uplink message during the TTIof the second duration. The operations of block 1815 may be performedaccording to the methods as described with reference to FIG. 2 . In someexamples, aspects of the operations of block 1815 may be performed by atransmitter as described with reference to FIGS. 9 through 11 .

FIG. 19 shows a flowchart illustrating a method 1900 for multiple TTIcoordination within a TDD configuration in accordance with variousaspects of the present disclosure. The operations of method 1900 may beimplemented by a base station 105 or its components as described herein.For example, the operations of method 1900 may be performed by a basestation TTI coordination manager as described with reference to FIGS. 13through 15 . In some examples, a base station 105 may execute a set ofcodes to control the functional elements of the device to perform thefunctions described below. Additionally or alternatively, the basestation 105 may perform aspects the functions described below usingspecial-purpose hardware.

At block 1905, the base station 105 may transmit first data during afirst TTI of the second duration and second data during a second TTI ofthe second duration. The operations of block 1905 may be performedaccording to the methods as described with reference to FIG. 2 . In someexamples, aspects of the operations of block 1905 may be performed by atransmitter as described with reference to FIGS. 13 through 15 .

At block 1910, the base station 105 may identify an uplink TTI of thefirst duration in the TDD configuration based on a feedback timingassociated with TTIs of the second duration. The operations of block1910 may be performed according to the methods as described withreference to FIG. 2 . In some examples, aspects of the operations ofblock 1910 may be performed by a feedback timing component as describedwith reference to FIGS. 13 through 15 .

At block 1915, the base station 105 may receive first feedback for thefirst data and second feedback for the second data during the uplink TTIof the first duration. The operations of block 1915 may be performedaccording to the methods as described with reference to FIG. 2 . In someexamples, aspects of the operations of block 1915 may be performed by areceiver as described with reference to FIGS. 13 through 15 .

FIG. 20 shows a flowchart illustrating a method 2000 for multiple TTIcoordination within a TDD configuration in accordance with variousaspects of the present disclosure. The operations of method 2000 may beimplemented by a base station 105 or its components as described herein.For example, the operations of method 2000 may be performed by a basestation TTI coordination manager as described with reference to FIGS. 13through 15 . In some examples, a base station 105 may execute a set ofcodes to control the functional elements of the device to perform thefunctions described below. Additionally or alternatively, the basestation 105 may perform aspects the functions described below usingspecial-purpose hardware.

At block 2005, the base station 105 may restrict one or more TTIs of thefirst duration in the TDD configuration for communication with a subsetof user equipment (UEs) in the system based on a delay metric. Theoperations of block 2005 may be performed according to the methods asdescribed with reference to FIG. 2 . In some examples, aspects of theoperations of block 2005 may be performed by a scheduling restrictioncomponent as described with reference to FIGS. 13 through 15 .

At block 2010, the base station 105 may schedule the subset of UEsaccording to the restriction of the one or more TTIs of the firstduration. The operations of block 2010 may be performed according to themethods as described with reference to FIG. 2 . In some examples,aspects of the operations of block 2010 may be performed by a schedulingcomponent as described with reference to FIGS. 13 through 15 .

At block 2015, the base station 105 may communicate with the subset ofUEs in one or more TTIs of the second duration based on the scheduling.The operations of block 2015 may be performed according to the methodsas described with reference to FIG. 2 . In some examples, aspects of theoperations of block 2015 may be performed by a transmitter as describedwith reference to FIGS. 13 through 15 .

FIG. 21 shows a flowchart illustrating a method 2100 for multiple TTIcoordination within a TDD configuration in accordance with variousaspects of the present disclosure. The operations of method 2100 may beimplemented by a base station 105 or its components as described herein.For example, the operations of method 2100 may be performed by a basestation TTI coordination manager as described with reference to FIGS. 13through 15 . In some examples, a base station 105 may execute a set ofcodes to control the functional elements of the device to perform thefunctions described below. Additionally or alternatively, the basestation 105 may perform aspects the functions described below usingspecial-purpose hardware.

At block 2105, the base station 105 may identify an UpPTS of a specialTTI of the first duration in the TDD configuration. The operations ofblock 2105 may be performed according to the methods as described withreference to FIG. 2 . In some examples, aspects of the operations ofblock 2105 may be performed by a special subframe component as describedwith reference to FIGS. 13 through 15 .

At block 2110, the base station 105 may identify a TTI of the secondduration during the UpPTS. The operations of block 2110 may be performedaccording to the methods as described with reference to FIG. 2 . In someexamples, aspects of the operations of block 2110 may be performed by aspecial subframe component as described with reference to FIGS. 13through 15 .

At block 2115, the base station 105 may receive an uplink control ordata message during the TTI of the second duration from a first UE. Theoperations of block 2115 may be performed according to the methods asdescribed with reference to FIG. 2 . In some examples, aspects of theoperations of block 2115 may be performed by a receiver as describedwith reference to FIGS. 13 through 15 .

In some examples, aspects from two or more of the methods may becombined. It should be noted that the methods are just exampleimplementations, and that the operations of the methods may berearranged or otherwise modified such that other implementations arepossible.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), FDMA, OFDMA, SC-FDMA, and othersystems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asCDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases may becommonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as Global System forMobile Communications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunications system (UMTS). 3GPP LTE andLTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA,E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from theorganization named “3rd Generation Partnership Project” (3GPP). CDMA2000and UMB are described in documents from an organization named “3rdGeneration Partnership Project 2” (3GPP2). The techniques describedherein may be used for the systems and radio technologies mentionedabove as well as other systems and radio technologies. While aspects anLTE system may be described for purposes of example, and LTE terminologymay be used in much of the description, the techniques described hereinare applicable beyond LTE applications.

In LTE/LTE-A networks, including such networks described herein, theterm evolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-A network in which different typesof evolved node B (eNBs) provide coverage for various geographicalregions. For example, each eNB or base station may provide communicationcoverage for a macro cell, a small cell, or other types of cell. Theterm “cell” is a 3GPP term that can be used to describe a base station,a carrier or component carrier associated with a base station, or acoverage area (e.g., sector, etc.) of a carrier or base station,depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an accesspoint, a radio transceiver, a NodeB, eNodeB (eNB), Home NodeB, a HomeeNodeB, or some other suitable terminology. The geographic coverage areafor a base station may be divided into sectors making up only a portionof the coverage area. The wireless communications system or systemsdescribed herein may include base stations of different types (e.g.,macro or small cell base stations). The UEs described herein may be ableto communicate with various types of base stations and network equipmentincluding macro eNBs, small cell eNBs, relay base stations, and thelike. There may be overlapping geographic coverage areas for differenttechnologies.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base station, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers). A UE may be able to communicate with varioustypes of base stations and network equipment including macro eNBs, smallcell eNBs, relay base stations, and the like.

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The downlink transmissions described herein may also be called forwardlink transmissions while the uplink transmissions may also be calledreverse link transmissions. Each communication link describedherein—including, for example, wireless communications system 100 and200 as described with reference to FIGS. 1 and 2 —may include one ormore carriers, where each carrier may be a signal made up of multiplesub-carriers (e.g., waveform signals of different frequencies).

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), an ASIC, afield-programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope and spirit of the disclosure and appended claims. For example,due to the nature of software, functions described above can beimplemented using software executed by a processor, hardware, firmware,hardwiring, or combinations of any of these. Features implementingfunctions may be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations. As used herein, including in the claims,the term “and/or,” when used in a list of two or more items, means thatany one of the listed items can be employed by itself, or anycombination of two or more of the listed items can be employed. Forexample, if a composition is described as containing components A, B,and/or C, the composition can contain A alone; B alone; C alone; A and Bin combination; A and C in combination; B and C in combination; or A, B,and C in combination. Also, as used herein, including in the claims,“or” as used in a list of items (for example, a list of items prefacedby a phrase such as “at least one of” or “one or more of”) indicates aninclusive list such that, for example, a phrase referring to “at leastone of” a list of items refers to any combination of those items,including single members. As an example, “at least one of: A, B, or C”is intended to cover A, B, C, A-B, A-C, B-C, and A-B-C., as well as anycombination with multiples of the same element (e.g., A-A, A-A-A, A-A-B,A-A-C, A-B-B, A-C-C, B-B, B-B-B, B-B-C, C-C, and C-C-C or any otherordering of A, B, and C).

As used herein, the phrase “based on” shall not be construed as areference to a closed set of conditions. For example, an exemplary stepthat is described as “based on condition A” may be based on both acondition A and a condition B without departing from the scope of thepresent disclosure. In other words, as used herein, the phrase “basedon” shall be construed in the same manner as the phrase “based at leastin part on.”

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media cancomprise RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, DSL, orwireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include CD, laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. The words “module,” “mechanism,”“element,” “device,” “component,” and the like may not be a substitutefor the word “means.” As such, no claim element is to be construed as ameans plus function unless the element is expressly recited using thephrase “means for.”

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication in a systemthat supports a time division duplexing (TDD) configuration withtransmission time intervals (TTIs) of a first duration and TTIs of asecond duration that is less than the first duration, comprising:determining a plurality of uplink symbols in a first TTI of the firstduration in the TDD configuration; determining a second TTI of thesecond duration during the plurality of uplink symbols in the first TTI;scheduling a user equipment (UE) for an uplink transmission during thesecond TTI of the second duration on a portion of the plurality ofuplink symbols in the first TTI, the portion of the plurality of uplinksymbols in the first TTI being different from a sounding referencesignal (SRS) portion of the plurality of uplink symbols in the firstTTI; and receiving an uplink acknowledgement message, responsive to adownlink message, during the second TTI of the second duration and onthe portion of the plurality of uplink symbols in the first TTIdifferent from the SRS portion of the plurality of uplink symbols in thefirst TTI.
 2. The method of claim 1, further comprising: determining aguard period during the first TTI of the first duration; determining anadditional TTI of the second duration during the guard period; andreceiving an additional uplink message during the additional TTI of thesecond duration.
 3. The method of claim 1, further comprising: receivingthe uplink acknowledgement message during a time period that comprisesthe portion of the plurality of uplink symbols in the first TTIdifferent from the SRS portion of the plurality of uplink symbols in thefirst TTI and a portion of an uplink TTI of the first duration in theTDD configuration.
 4. The method of claim 1, further comprising:determining one or more downlink symbols in a third TTI, wherein thethird TTI is of the first duration in the TDD configuration.
 5. Themethod of claim 4, wherein the plurality of uplink symbols in the firstTTI and the one or more downlink symbols in the third TTI are includedin a special subframe or slot.
 6. The method of claim 1, furthercomprising: receiving a SRS, from a second UE different from the UE, onthe SRS portion of the plurality of uplink symbols in the first TTI. 7.The method of claim 1, wherein the first TTI comprises one or moreslots, each slot comprising two or more symbols of the plurality ofuplink symbols.
 8. An apparatus for wireless communication in a systemthat supports a time division duplexing (TDD) configuration withtransmission time intervals (TTIs) of a first duration and TTIs of asecond duration that is less than the first duration, comprising: aprocessor; memory coupled with the processor; and instructions stored inthe memory and operable, when executed by the processor, to cause theapparatus to: determine a plurality of uplink symbols in a first TTI ofthe first duration in the TDD configuration; determine a second TTI ofthe second duration during the plurality of uplink symbols in the firstTTI; schedule a user equipment (UE) for an uplink transmission duringthe second TTI of the second duration on a portion of the plurality ofuplink symbols in the first TTI, the portion of the plurality of uplinksymbols in the first TTI being different from a sounding referencesignal (SRS) portion of the plurality of uplink symbols in the firstTTI; and receive an uplink acknowledgement message, responsive to adownlink message, during the second TTI of the second duration and onthe portion of the plurality of uplink symbols in the first TTIdifferent from the SRS portion of the plurality of uplink symbols in thefirst TTI.
 9. The apparatus of claim 8, further comprising instructionsstored in the memory and executable by the processor to cause theapparatus to: determine a guard period during the first TTI of the firstduration; determine an additional TTI of the second duration during theguard period; and receive an additional uplink message during theadditional TTI of the second duration.
 10. The apparatus of claim 8,further comprising instructions stored in the memory and executable bythe processor to cause the apparatus to: receive the uplinkacknowledgement message during a time period that comprises the portionof the plurality of uplink symbols in the first TTI different from theSRS portion of the plurality of uplink symbols in the first TTI and aportion of an uplink TTI of the first duration in the TDD configuration.11. The apparatus of claim 8, further comprising instructions stored inthe memory and executable by the processor to cause the apparatus to:determine one or more downlink symbols in a third TTI, wherein the thirdTTI is of the first duration in the TDD configuration.
 12. The apparatusof claim 11, wherein the plurality of uplink symbols in the first TTIand the one or more downlink symbols in the third TTI are included in aspecial subframe or slot.
 13. The apparatus of claim 8, furthercomprising instructions stored in the memory and executable by theprocessor to cause the apparatus to: receive a SRS, from a second UEdifferent from the UE, on the SRS portion of the plurality of uplinksymbols in the first TTI.
 14. The apparatus of claim 8, wherein thefirst TTI comprises one or more slots, each slot comprising two or moresymbols of the plurality of uplink symbols.
 15. A non-transitorycomputer-readable medium storing code for wireless communication in asystem that supports a time division duplexing (TDD) configuration withtransmission time intervals (TTIs) of a first duration and TTIs of asecond duration that is less than the first duration, the codecomprising instructions executable by a processor to: determine aplurality of uplink symbols in a first TTI of the first duration in theTDD configuration; determine a second TTI of the second duration duringthe plurality of uplink symbols in the first TTI; schedule a userequipment (UE) for an uplink transmission during the second TTI of thesecond duration on a portion of the plurality of uplink symbols in thefirst TTI, the portion of the plurality of uplink symbols in the firstTTI being different from a sounding reference signal (SRS) portion ofthe plurality of uplink symbols in the first TTI; and receive an uplinkacknowledgement message, responsive to a downlink message, during thesecond TTI of the second duration and on the portion of the plurality ofuplink symbols in the first TTI different from the SRS portion of theplurality of uplink symbols in the first TTI.
 16. The non-transitorycomputer-readable medium of claim 15, wherein the instructions arefurther executable to: determine a guard period during the first TTI ofthe first duration; determine an additional TTI of the second durationduring the guard period; and receive an additional uplink message duringthe additional TTI of the second duration.
 17. The non-transitorycomputer-readable medium of claim 15, wherein the instructions arefurther executable to: receive the uplink acknowledgement message duringa time period that comprises the portion of the plurality of uplinksymbols in the first TTI different from the SRS portion of the pluralityof uplink symbols in the first TTI and a portion of an uplink TTI of thefirst duration in the TDD configuration.
 18. The non-transitorycomputer-readable medium of claim 15, wherein the instructions arefurther executable to: determine one or more downlink symbols in a thirdTTI, wherein the third TTI is of the first duration in the TDDconfiguration.
 19. The non-transitory computer-readable medium of claim18, wherein the plurality of uplink symbols in the first TTI and the oneor more downlink symbols in the third TTI are included in a specialsubframe or slot.
 20. The non-transitory computer-readable medium ofclaim 15, wherein the instructions are further executable to: receive aSRS, from a second UE different from the UE, on the SRS portion of theplurality of uplink symbols in the first TTI.
 21. An apparatus forwireless communication in a system that supports a time divisionduplexing (TDD) configuration with transmission time intervals (TTIs) ofa first duration and TTIs of a second duration that is less than thefirst duration, comprising: means for determining a plurality of uplinksymbols in a first TTI of the first duration in the TDD configuration;means for determining a second TTI of the second duration during theplurality of uplink symbols in the first TTI; means for scheduling auser equipment (UE) for an uplink transmission during the second TTI ofthe second duration on a portion of the plurality of uplink symbols inthe first TTI, the portion of the plurality of uplink symbols in thefirst TTI being different from a sounding reference signal (SRS) portionof the plurality of uplink symbols in the first TTI; and means forreceiving an uplink acknowledgement message, responsive to a downlinkmessage, during the second TTI of the second duration and on the portionof the plurality of uplink symbols in the first TTI different from theSRS portion of the plurality of uplink symbols in the first TTI.
 22. Theapparatus of claim 21, further comprising: means for determining a guardperiod during the first TTI of the first duration; means for determiningan additional TTI of the second duration during the guard period; andmeans for receiving an additional uplink message during the additionalTTI of the second duration.
 23. The apparatus of claim 21, furthercomprising: means for receiving the uplink acknowledgement messageduring a time period that comprises the portion of the plurality ofuplink symbols in the first TTI different from the SRS portion of theplurality of uplink symbols in the first TTI and a portion of an uplinkTTI of the first duration in the TDD configuration.
 24. The apparatus ofclaim 21, further comprising: means for determining one or more downlinksymbols in a third TTI, wherein the third TTI is of the first durationin the TDD configuration.
 25. The apparatus of claim 24, wherein theplurality of uplink symbols in the first TTI and the one or moredownlink symbols in the third TTI are included in a special subframe orslot.
 26. The apparatus of claim 21, further comprising: means forreceiving a SRS, from a second UE different from the UE, on the SRSportion of the plurality of uplink symbols in the first TTI.
 27. Theapparatus of claim 21, wherein the first TTI comprises one or moreslots, each slot comprising two or more symbols of the plurality ofuplink symbols.
 28. A method for wireless communication in a system thatsupports a time division duplexing (TDD) configuration with transmissiontime intervals (TTIs) of a first duration and TTIs of a second durationthat is less than the first duration, comprising: identifying aplurality of uplink symbols in a first TTI of the first duration in theTDD configuration; identifying a second TTI of the second durationduring the plurality of uplink symbols in the first TTI and an uplinktransmission scheduled for a portion of the plurality of uplink symbolsin the first TTI, the portion of the plurality of uplink symbols in thefirst TTI being different from a sounding reference signal (SRS) portionof the plurality of uplink symbols in the first TTI; and transmitting anuplink acknowledgement message, responsive to a downlink message, duringthe second TTI of the second duration and on the portion of theplurality of uplink symbols in the first TTI different from the SRSportion of the plurality of uplink symbols in the first TTI.
 29. Themethod of claim 28, further comprising: identifying a guard periodduring the first TTI of the first duration; identifying an additionalTTI of the second duration during the guard period; and transmitting anadditional uplink message during the additional TTI of the secondduration.
 30. The method of claim 28, further comprising: transmittingthe uplink acknowledgement message during a time period that comprisesthe portion of the plurality of uplink symbols in the first TTIdifferent from the SRS portion of the plurality of uplink symbols in thefirst TTI and a portion of an uplink TTI of the first duration in theTDD configuration.
 31. The method of claim 28, further comprising:identifying one or more downlink symbols in a third TTI, wherein thethird TTI is of the first duration in the TDD configuration.
 32. Themethod of claim 31, wherein the plurality of uplink symbols in the firstTTI and the one or more downlink symbols in the third TTI are includedin a special subframe or slot.
 33. The method of claim 28, wherein thefirst TTI comprises one or more slots, each slot comprising two or moresymbols of the plurality of uplink symbols.
 34. An apparatus forwireless communication in a system that supports a time divisionduplexing (TDD) configuration with transmission time intervals (TTIs) ofa first duration and TTIs of a second duration that is less than thefirst duration, comprising: a processor; memory coupled with theprocessor; and instructions stored in the memory and operable, whenexecuted by the processor, to cause the apparatus to: identify aplurality of uplink symbols in a first TTI of the first duration in theTDD configuration; identify a second TTI of the second duration duringthe plurality of uplink symbols in the first TTI and an uplinktransmission scheduled for a portion of the plurality of uplink symbolsin the first TTI, the portion of the plurality of uplink symbols in thefirst TTI being different from a sounding reference signal (SRS) portionof the plurality of uplink symbols in the first TTI; and transmit anuplink acknowledgement message, responsive to a downlink message, duringthe second TTI of the second duration and on the portion of theplurality of uplink symbols in the first TTI different from the SRSportion of the plurality of uplink symbols in the first TTI.
 35. Theapparatus of claim 34, further comprising instructions stored in thememory and executable by the processor to cause the apparatus to:identify a guard period during the first TTI of the first duration;identify an additional TTI of the second duration during the guardperiod; and transmit an additional uplink message during the additionalTTI of the second duration.
 36. The apparatus of claim 34, furthercomprising instructions stored in the memory and executable by theprocessor to cause the apparatus to: transmit the uplink acknowledgementmessage during a time period that comprises the portion of the pluralityof uplink symbols in the first TTI different from the SRS portion of theplurality of uplink symbols in the first TTI and a portion of an uplinkTTI of the first duration in the TDD configuration.
 37. The apparatus ofclaim 34, further comprising instructions stored in the memory andexecutable by the processor to cause the apparatus to: identify one ormore downlink symbols in a third TTI, wherein the third TTI is of thefirst duration in the TDD configuration.
 38. The apparatus of claim 37,wherein the plurality of uplink symbols in the first TTI and the one ormore downlink symbols in the third TTI are included in a specialsubframe or slot.
 39. The apparatus of claim 34, wherein the first TTIcomprises one or more slots, each slot comprising two or more symbols ofthe plurality of uplink symbols.
 40. A non-transitory computer-readablemedium storing code for wireless communication in a system that supportsa time division duplexing (TDD) configuration with transmission timeintervals (TTIs) of a first duration and TTIs of a second duration thatis less than the first duration, the code comprising instructionsexecutable by a processor to: identify a plurality of uplink symbols ina first TTI of the first duration in the TDD configuration; identify asecond TTI of the second duration during the plurality of uplink symbolsin the first TTI and an uplink transmission scheduled for a portion ofthe plurality of uplink symbols in the first TTI, the portion of theplurality of uplink symbols in the first TTI being different from asounding reference signal (SRS) portion of the plurality of uplinksymbols in the first TTI; and transmit an uplink acknowledgementmessage, responsive to a downlink message, during the second TTI of thesecond duration and on the portion of the plurality of uplink symbols inthe first TTI different from the SRS portion of the plurality of uplinksymbols in the first TTI.
 41. The non-transitory computer-readablemedium of claim 40, wherein the instructions are further executable to:identify a guard period during the first TTI of the first duration;identify an additional TTI of the second duration during the guardperiod; and transmit an additional uplink message during the additionalTTI of the second duration.
 42. The non-transitory computer-readablemedium of claim 40, wherein the instructions are further executable to:transmit the uplink acknowledgement message during a time period thatcomprises the portion of the plurality of uplink symbols in the firstTTI different from the SRS portion of the plurality of uplink symbols inthe first TTI and a portion of an uplink TTI of the first duration inthe TDD configuration.
 43. The non-transitory computer-readable mediumof claim 40, wherein the instructions are further executable to:identify one or more downlink symbols in a third TTI, wherein the thirdTTI is of the first duration in the TDD configuration.
 44. Thenon-transitory computer-readable medium of claim 43, wherein theplurality of uplink symbols in the first TTI and the one or moredownlink symbols in the third TTI are included in a special subframe orslot.
 45. An apparatus for wireless communication in a system thatsupports a time division duplexing (TDD) configuration with transmissiontime intervals (TTIs) of a first duration and TTIs of a second durationthat is less than the first duration, comprising: means for identifyinga plurality of uplink symbols in a first TTI of the first duration inthe TDD configuration; means for identifying a second TTI of the secondduration during the plurality of uplink symbols in the first TTI and anuplink transmission scheduled for a portion of the plurality of uplinksymbols in the first TTI, the portion of the plurality of uplink symbolsin the first TTI being different from a sounding reference signal (SRS)portion of the plurality of uplink symbols in the first TTI; and meansfor transmitting an uplink acknowledgement message, responsive to adownlink message, during the second TTI of the second duration and onthe portion of the plurality of uplink symbols in the first TTIdifferent from the SRS portion of the plurality of uplink symbols in thefirst TTI.
 46. The apparatus of claim 45, further comprising: means foridentifying a guard period during the first TTI of the first duration;means for identifying an additional TTI of the second duration duringthe guard period; and means for transmitting an additional uplinkmessage during the additional TTI of the second duration.
 47. Theapparatus of claim 45, further comprising: means for transmitting theuplink acknowledgement message during a time period that comprises theportion of the plurality of uplink symbols in the first TTI differentfrom the SRS portion of the plurality of uplink symbols in the first TTIand a portion of an uplink TTI of the first duration in the TDDconfiguration.
 48. The apparatus of claim 45, further comprising: meansfor identifying one or more downlink symbols in a third TTI, wherein thethird TTI is of the first duration in the TDD configuration.
 49. Theapparatus of claim 48, wherein the plurality of uplink symbols in thefirst TTI and the one or more downlink symbols in the third TTI areincluded in a special subframe or slot.
 50. The apparatus of claim 45,wherein the first TTI comprises one or more slots, each slot comprisingtwo or more symbols of the plurality of uplink symbols.